Le séquoia à feuilles d'if (Sequoia sempervirens), le plus haut arbre du monde
Le séquoia à feuilles d'if (Sequoia sempervirens
) est une de trois espèces de séquoia, comme le séquoia géant (Sequoiadendron giganteum)
et le séquoia de Chine (Metasequoia glyptostroboides)
L'arbre le plus haut du monde
est un exemplaire de cette espèce.
Son habitat naturel est une bande étroite de 750 km de long et 75 km de large le long de la côte Pacifique des États-Unis, de 0 à 900 m d'altitude. Les arbres les plus imposants poussent dans des vallées très arrosées avec de nombreuses périodes de brouillard.
Avec une forme plus svelte le séquoia à feuilles d'if peut atteindre des hauteurs plus de 20 m plus que celles du séquoia géant, qui est quand-même l'arbre le plus volumineux du monde.
Le plus haut spécimen de Sequoia sempervirens, Hypérion, mesure 115,55 mètres!
Une hauteur comme ça est prèsque 120 à 130 m, une hauteur qui est l'hauteur maximal pour des arbres selon une récherche scientifique de 2004.
Les forêts côtieres humides de Californie
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During the whole year it rains quite a lot in this thin coastal strip and it is quite foggy most of the time.
This way the tree can absorb enough water and does not suffer that much from evaporation stress. Most of the tallest trees can be found in the wet river valleys on fertile, alluvial deposits, although unexpectedly a couple of recently discovered record breaking trees appeared to grow on the valley slopes.
The coast redwood forests have an abundant undergrowth (amongst which there are a lot of ferns). However, the biggest biodiversity can be found tens of meters up: differents species of plants, lichens, salamanders, ... live high up in the sky between the complex branch systems of the redwoods.
Prof. Steve Sillett, who studies these redwood canopies, compares them with "hanging gardens".
The get an impression of the size of these redwoods: the images above show some of these trees.
On the left is the "Del Norte Titan" in the Jedediah Smith Redwoods State Park, California (© Robert Van Pelt). Notice the people in the left bottom corner. The tree on the right is called "Screaming Titans", also in Jedediah Smith Redwoods State Park.
The Del Norte Titan has a height of 93.6 m and a girth at breast height of 22.7 m. He is definitely not the tallest coast redwood, or the thickest, but has the second largest trunk volume ("The Lost Monarch" comes in first, depending on your definition of a "single tree"). Nevertheless he is surpassed in volume by the giant sequoia (Sequoiadendron), of which about fifteen specimens have a bigger volume with "General Sherman" on top of the list.
On first sight, the needles of the coast redwood do not resemble those of the giant sequoia: they are bigger and flat, much like that of a yew. The crown is conical just like the one of the giant redwood, with an almost equally massive trunk with a reddish brown, soft bark. The egg shaped cones are smaller (2 to 3 cm). In contrast to most other conifers, the coast redwood starts to grow again after being cut. The maximum age is probably around 2500 years.
Heavily threatened by logging companies
This quickly growing tree has straight trunks and the quality of the wood is excellent, which resulted in heavy - and ongoing - loggings.
The wood of Sequoia sempervirens
has been and is extensively used in construction. About 96% of the original redwood forests have been logged and the deforestation is still continuing. Luckily most of the few remaining stands are preserved in the National and State Parks, which are probably essential for the long term preservation of this species.
The woods outside of the parks (with many trees more than a thousand years old) are still being "commercially managed"....
This is source of constant protests, such as the famous action of activist Julia Butterfly Hill (photo).
For over two years, she lived in the canopy of a coast redwood named "Luna" to keep the the old growth tree from being logged by the Pacific Lumber Company and to plead for sustainable forestry instead of clearcutting entire woods (which has devastating effects on the natural balance and causes extreme soil erosion).
Eventually she succeeded: as a result of the massive press coverage (and the attention for the old growth forest clearcuttings it brought with it) "Luna" and some other redwoods were saved from the chain saw. What a remarkable woman!
It's highly probable that without actions like that and protests of organisations like "Save the redwoods League", "Sempervirens Fund", "Sierra Club", and others, there would be no old growth redwood forests left.
These organisations get their money from gifts and buy privaty property themselves to donate them to the State Parks and National Parks.
The images below were taken by Nick Sabadosh in the misty redwood woods near Crescent City, California an are used here with permission . These holiday photos show specimens of Sequoia sempervirens in their natural environment, the foggy forests near the Pacific.
Because of the dramatic atmosphere, these forests have been used as scenery in movies: the scenes with the Ewoks in the Star Wars movies were shot in these woods, just as multiple parts of the Jurassic Park movies.
For those last movies this choice is not very unlogic: during the Cretaceous, the top period for North American dinosaurs, these woods could be found all over the continent.
These trees (and especially young ones) are quite sensitive for winter frost and do not grow that well on the eastern side of the Rockies and in most parts of Europe.
Biggest limiting factor is drought: it just isn't wet enough. In the wettest European parts, in England and Wales, planted redwoods do already reach 45 meters and more en seed themselves.
Most of the groves are located in the coastal area of California. The largest populations are in Jedediah Smith Redwoods State Park (Del Norte County), Redwood National Park and Humboldt Redwoods State Park (Humboldt County).
The most visited grove is in Muir Woods National Monument, one of the last remaining stands in the immediate San Francisco Bay Area.
The tallest tree in the world
Hyperion, the world's tallest living tree, is a coast redwood and is no less than 379.1 ft
(115.55 m) tall!
This enormous tree was discovered only in August 2006 in a remote part of the Redwood National Park, California.
- "The limits to tree height", Koch et al. Letters to Nature, avril 2004 (pdf)
- "New tallest tree discovered!", Robert Van Pelt, 26 août 2006
- BBC News: giant tree devastated by fire
- Nick Sabadosh' weblog
- The New Yorker, article "Tall for its age", Richard Preston, 6 octobre 2006 (pdf)
(D. Don) Endlicher 1847.
Synonymes: Taxodium sempervirens
D. Don in Lambert 1824 (Watson 1993), Sequoia sempervirens
(Lambert) Endlicher (Peattie 1950).
Il est le seul espèce dans le genre Sequoia
Endlicher 1847. Quelques variétés cultivées existent comme le cultivar 'adpressa', 'glauca', 'nana pendula', 'pendula' ou 'prostrata'.
Plus sur les deux autres espèces de séquoia: le séquoia géant (Sequoiadendron giganteum) et le séquoia de Chine (Metasequoia glyptostroboides).
Plus sur les arbres les plus gros et les plus anciens du monde.